Containers, and more specifically metallic beverage containers, generally contain a neck or an upper portion that is adapted for interconnection to a metallic end closure. The container end closure is formed from a flat sheet of metallic material and generally includes a pull tab or other form of stay on tab (SOT). Beverage containers commonly store carbonated beverages, thus, both the container body and the container end closure are required to sustain internal pressures up to 90 psi without catastrophic failure or permanent deformation. Further, depending on the various conditions that the sealed container is exposed to heat, over fill, high CO2 content, vibration, etc., the internal pressure in a typical beverage container may at times exceed 90 psi. Thus, the container and end closure must be designed to resist deformation and failure while utilizing thin metallic materials.
Beverage containers are manufactured of thin and durable materials, such as aluminum, to decrease the overall cost of the manufacturing process and the weight of the finished product. It is also desirable to reduce the volume of material needed to fabricate the container end closure by optimizing the geometry and to more effectively improve buckle resistance and deformation. Accordingly, there exists a significant need for a durable beverage container end closure that can withstand high internal pressures associated with stored carbonated beverages and external forces applied during shipping, yet which is manufactured with durable, lightweight, reduced gage metallic materials with geometric configurations that reduce material requirements.
In an attempt to decrease material costs and improve strength, end closure engineers position the central panel proximate to the upper portion of the peripheral curl, which can result in other performance issues. More specifically, container end closures with a raised central panel height may experience problems associated with “tab-over-chime.” “Tab-over-chime” refers to a geometry where the pull tab is located above the height of the container, which creates stacking problems and thus potential damage during shipping and increased expenses. Thus, it is a challenge to design a container end closure that has improved geometry so that reduced gauge aluminum materials may be used while maintaining buckling and deformation performance of the end closure.
Previous attempts have been made to manufacture container end closures with unique geometric configuration in an attempt to provide material savings and improve strength. One example of a prior art beverage can end may be found in U.S. Pat. No. 7,100,789 to Nguyen et al., which is incorporated by reference in its entirety. Nguyen discloses a beverage container end closure that utilizes less material and has a chuck wall with improved buckle strength attributed to an inwardly oriented concave arch with a radius of curvature between about 0.015 inches and 0.080 inches. Container end closures that employ other unique geometries are disclosed in U.S. Pat. Nos. 7,506,779; 5,685,189; 6,460,723; 6,968,724 and U.S. Patent Application Publication Nos. 2002/015807 and 2005/0029269, which are each incorporated herein by reference.
The following disclosure describes an improved container end closure that is adapted for interconnection to a container body and that employs countersink and chuck wall geometry that decreases material costs while maintaining or improving performance.